Control Value vs Lockshield Valve Telling the difference

Hi I need to remove a raditator, however none of the valves either side of any of my radiators has any of the plastic covers on, meaning I cant tell which is the control valve and which one is the lockshield valve. Basically both ends looks the same, and both ends seem to have give in them when I turn them. How do I work out which one is which ?

It really does not matter as long as you turn them both off before removing the rad.